This invention relates to a solar energy system in general and more particularly to solar energy system utilizing lens systems to concentrate the rays of the sun.
In U.S. Pat. No. 4,134,393, of which I am a co-inventor and the sole assignee, and in pending application Ser. No. 807,513 filed June 20, 1977 and Ser. No. 845,862 filed Oct. 31, 1977 (now U.S. Pat. No. 4,194,948), of which I am sole inventor, solar energy distillation apparatus are disclosed in which a part of the heat of condensation of the condensing liquid is recovered. In the disclosed embodiments in those applications, the heat of condensation is transferred to a fluid in a fluid lens disposed over the liquid to be distilled inclined to provide a bottom surface on which the evaporated liquid is condensed and flows to be discharged fromthe lower end thereof.
At locations where a lens inclination of greater than 20.degree. is desirable to increase collection, the system operates at reduced efficiency since the fluid lens is limited to angles of inclination of less than about 20.degree..
Fluid lenses also have other drawbacks, which in accordance with my appliction Ser. No. 915,001, filed June 13, 1978, are substantially overcome and improved solar energy distillation apparatus obtained by providing solar distallation apparatus in which the solar energy is concentrated inthe liquid to be distilled and double plate conduit means, with an upper and a lower wall between which a heat exchange fluid flows are provided to condense the evaporated liquid vapor on a surface thereof, the conduit means being disposed intermediate the liquid to be distilled and lens means for concentrating the solar energy in the liquid.
The concentrated solar energy causes the liquid to evaporate with the vapor impinging and being condensed upon the outer surface of the lower wall of the conduit means, the condensed liquid flowing along the outer surface of the lower wall to the lower end thereof and falling therefrom into a container, a substantial part of the heat of condensation of the condensing vapor being absorbed by the fluid in the conduit means.
According to one embodiment of Ser. No. 915,001, the lens means comprise a plurality of sets or series of Fresnel-type lenses arranged to provide an elongated narrow focus. The container includes a plurality of baffles dividing the container interior into a plurality of distillation compartments for the liquid to be distilled and is inclined so that the compartments are offset in height. The elongated focus of each series of Fresnel lenses may therefore be located in and along a different compartment.
An expansion tank for the heat exchange fluid in the conduit is located so as to provide minimal pressure within the conduit.
A heat exchanger is also provided to transfer the heat recovered in the heat exchange fluid circulated in the conduit to the liquid being introduced into the container to preheat the liquid. The heat exchanger is also located to minimize pressure in the conduit.
In accordance with another disclosed embodiment of Ser. No. 915,001, the sets of Fresnel lenses are arranged so that the elongated focus of at least one set is substantially parallel to the axes of the compartments in the container and the elongated focus of at least one other set is arranged so that the elongated focus is transverse to the axes of the compartments and extends into varying depths of liquid in the container. The two sets of Fresnel lenses are arranged at an angle to each other so that they meet along an apex with each set having a lower end.
According to another aspect of that disclosure, the bottom of the compartment containing the liquid to be distilled is blackened to allow absorption of solar energy and enhance the heating of the liquid.
Furthermore, in my co-pending application Ser. No. 920,288 filed June 29, 1978, solar energy is concentrated by lens means in an elongated focus located substantially in or on the surface of, and substantially along at least one conduit system by a lens means which is pivoted at least about a first axis of the least one conduit. The conduit system includes an inner conduit enclosed by an enclosure with the enclosed inner conduit and enclosure enclosed by an outer conduit. A collector having inner and outer conduits which are transparent at least in part with photovoltaic cells disposed in the inner conduit and a fluid which absorbs substantial amounts of infrared solar energy circulated in the outer conduit is utilized.
In accordance with Ser. No. 920,288, the apparatus is disposed so the first axis extends generally in the North-South direction, so that the lens means can track the sun on a daily basis, the conduit remaining stationary as the lens means is pivoted.
According to that disclosure, the lens means comprises at least one Fresnel lens having prisms extending substantially parallel to the first axis.
In one embodiment disclosed therein the apparatus comprises a plurality of adjacently disposed collectors and a plurality of adjacently disposed lens means. According to this embodiment, the lens means and collectors are pivoted about an axis only on a daily basis with the at least one conduit remaining stationary regardless of season.
In accordance with still another aspect of that invention, an elongated conduit system for collecting solar energy in an elongated focus is provided in which the elongated focus is located substantially in or on and substantially along the conduit system, which comprises two elongated conduits for passing fluids therethrough and an enclosure for a first of the conduits, the conduits and enclosure being disposed so that an inner of the conduits containing a fluid therein is enclosed by the enclosure, there being a dead space in the enclosure surrounding the inner conduit, and an outer of the conduits containing a fluid therein encloses the enclosure and inner conduit, at least part of the enclosure and outer conduit being transparent with transparent portions thereof being aligned and adapted to transmit the solar energy in the elongated focus therethrough. The inner conduit is opaque with a darkened outer surface and the dead space in the enclosure preferably contains air, the elongated focus being located substantially on and substantially along the outer surface of the inner conduit which absorbs the solar energy and transmits heat to the fluid therein. In the preferred embodiment, the inner conduit comprises metal piping and the enclosure and outer conduit comprise glass tubing. The inner and outer conduits carry heat exchange fluids while the dead space around the inner conduit provides insulation for the fluid therein.
According to an aspect of my previous application Ser. No. 920,288, photovoltaic cells which produce electricity from luminous solar energy of about 0.4 to about 0.7 microns wavelength are installed in an inner conduit which is transparent at least in part of an elongated collector. The elongated focus of a Fresnel lens is located on the cells in the inner conduit. The inner conduit is enclosed by an outer conduit which is transparent at least in part.
This arrangement increases the production of electricity by the photovoltaic cells since their efficiency is not substantially reduced by the heat that would be generated by infrared solar energy otherwise reaching the cells. In the preferred embodiment, the fluid is water.